1. Technical Field
The invention relates to enhanced hematopoietic stem and progenitor cells and therapeutic compositions comprising the enhanced cells. The invention also relates to methods of making the enhanced hematopoietic and progenitor cells and therapeutic compositions and methods of use thereof, including use for reconstituting the hematopoietic system of an individual and treating conditions and diseases associated with ischemia.
2. Description of the Related Art
The goal of regenerative medicine is to maintain, improve or even restore the function of damaged or diseased cells, tissues, and organs. One way that regenerative medicine aims to revolutionize the practice of medicine is to employ cell-based therapeutics to treat patients. However, for the promise of cell-based therapeutics to be fully realized, the therapeutic cells should be well-tolerated when introduced into a patient, the cells should also migrate or “home” to sites where therapy is needed, and the cells should be capable of providing the therapy desired. The art has attempted to employ stem cell- and progenitor cell-based therapeutics but has met with little, if any, success in a human clinical setting.
One area of regenerative medicine that would benefit from improved cell-based therapeutics are stem cell transplants, e.g., bone marrow transplants and hematopoietic stem cell transplants to treat various genetic diseases, cancers, and degenerative disorders. According to the National Marrow Donor Program® (NMDP), an estimated 45,000 to 50,000 hematopoietic cell transplants are performed annually worldwide to treat patients with life-threatening malignant and non-malignant diseases. However, bone marrow transplantation has numerous drawbacks: bone marrow donation is painful, at times it is difficult and time consuming, and often not possible, to find HLA donor matched tissue; and allogeneic transplants are associated with a significant incidence of graft-versus-host-disease (GVHD). Moreover, although allogeneic hematopoietic stem cell transplants have been performed using more easily obtainable umbilical cord blood, cord blood transplants still have a risk of GVHD. Other drawbacks to existing methods of cord blood transplants, include fewer numbers of transplantable cells and deficient homing and engraftment of donor cells, both of which put the patient at high risk for life threatening infections. In addition, cord blood transplants generally have all the same risks as marrow and peripheral blood transplants.
Numerous approaches have been tried to expand the number of human hematopoietic stem and progenitor cells in cord blood within isolated grafts in ex vivo settings, to reduce the incidence of GVHD, or to increase the ability of the cells to home and engraft, but these efforts have had limited success.
Another area of regenerative medicine that would benefit from improved cell-based therapeutics is the treatment of tissue damaged by ischemia. Disruption of blood flow to tissues and organs is known as ischemia. The viability of cells, tissues, and organs in the human body depends on adequate blood flow. Adequate blood flow provides cells with oxygen, glucose, and much needed nutrients that are important for the regulation of cellular physiology and metabolism. Ischemia can be acute or chronic. Both acute and chronic forms of ischemia result in the loss of adequate nutrients to the cells, and if prolonged, will result in hypoxic and/or anoxic conditions. If the ischemia is left untreated, the cells may undergo necrosis or apoptosis, thereby jeopardizing the integrity and health of the tissue or organ.
Ischemia affects millions of patients in the United States each year. Ischemia is caused by a virtually limitless variety of genetic conditions, environmental insults, traumatic injury, or surgical interventions. The most common types of ischemia patients suffer from include, but are not limited to cerebral ischemias, spinal cord injuries, cardiovascular ischemias, limb ischemias, intestinal ischemias, dermal ischemias (e.g., burns and frostbite wounds) and ischemias resulting from medical and surgical procedures, including, but not limited to organ transplants, and skin grafts.
Currently, resolution of acute and chronic ischemia requires restoration of tissue perfusion and blood flow often using surgical means, which further places patients as risk for ischemic tissue damage. Restoration of blood flow after a period of ischemia can actually be more damaging than the ischemia. Reintroduction of oxygen causes a greater production of damaging free radicals as well as allowing, via removal of the extracellular acidotic conditions, influx of calcium and thus calcium overloading. Overall this results in reperfusion injury which can result in potentially fatal cardiac arrhythmias, also necrosis can be greatly accelerated. Other existing treatments that address ischemic tissue include hyperbaric oxygen, intravenous thrombolytics, anti-inflammatory agents, and local application of angiogenesis promoters. However, these treatments have generally met with limited success, if any.
Thus, many of the cell-based compositions and materials used in regenerative medicine are currently cost-prohibitive, inefficient, and/or unsafe. Other significant shortcomings for the use of stem cell- and progenitor cell-based therapeutic in regenerative medicine are the lack of technologies available to control stem cell proliferation, mobility, or to direct the stem cell, e.g., homing, to the particular niche or tissue where the therapy is needed. The end result is that cell-based therapeutics are not considered a realistic treatment option for those in need of regenerative medicine.
Accordingly, there is a substantial need in the art for improved cell-based therapeutics that are expandable, that are able to home to sites in the patient where therapy is desired, and that are able to provide a persistent therapeutic benefit. The present invention addresses these needs and offers other related advantages.